sickle cell disease Flashcards
genetic difference
- instead of HbA patients have an abnormal variant called Hb S
- Hb S results in the sickle shape
- autosomal recessive
- effects gene for beta-globin on chromosome 11
- need 2 copies for the disease
- patients with only 1 are asymptomatic
screening
newborn blood spot test at about 5 days old
complications
- Anaemia
- Increased risk of infection
- Chronic kidney disease
- Sickle cell crises
- Acute chest syndrome
- Stroke
- Avascular necrosis in large joints such as the hip
- Pulmonary hypertension
- Gallstones
- Priapism (painful and persistent penile erections)
whats a sickle cell crisis and what exaccerbates it?
a spectrum of acute exaccerbations caused by sickle cell disease
- can be mild or life threateneing
exaccerbated:
- just spontaneously
- dehydration
- infection
- stress
- cold weather
management of sickle cell crisis
no specific treatment for this but can be managed by:
- Low threshold for admission to hospital
- Treating infections that may have triggered the crisis
- Keep warm
- Good hydration (IV fluids may be required)
- Analgesia (NSAIDs should be avoided where there is renal impairment)
acute complications of sickle cell
- Painful Vaso-Occlusive Crisis
- Dactylitis (inflammation of digit)
- stroke
- Hepatic / Splenic Sequestration
- Sepsis (Atypical Organisms)
- Acute Chest Syndrome
- Haemolytic Crises
- Aplastic Crises (Parvovirus B19)
name the sickle crises
- vaso-occlusive crisis
- splenic sequestration crisis
- aplastic crisis
- acute chest syndrome
Vaso-occlusive Crisis
- also known as painful crisis
- most common crisis
- RBC clog capillaries causing distal ishcemia
- pain and swelling in hands and feet but can affect other areas
- can cause priapism - urological emerggency
Splenic Sequestration Crisis
- RBC cause backflow within the spleen
- painful
- can lead to severe aneamia and hypovolaemic shock
- emergency
- blood transfucions and fluid fescusitation
- can lead to splenic infarction making infections more common
- splenectomy prevents crisis in recurrent cases
Aplastic Crisis
- causes temporary absense of new blood cells
- triggered by paravirus B19
- leads to severe anaemia
- supportive management with blood transfusions if nessesary
Acute Chest Syndrome
- occurs when vessels supplying lungs become clogged with RBC
- caused by vaso-occulative crisis, fat embolism or infection
- pulmonary infiltrates on xray
- medical emergency
whys hydroxycarbamide sometimes given in management
- stimuates fetal haemoglobin HbF
- this doesnt lead to sickling
whys crizanlizumab sometimes given in the management of sickle
- its a monoclonal antibody
- targets P-selectin which is an adhesion molecule on the endothelium
- prevents RBC from sticking
Another common complication of sickle cell anaemia (2)
- Osteomyelitis
- Usually due to s.aureus, but in those patients = salmonella
Diagnosis of sickle cell anaemia (4)
- Sickle solubility test
- Newborn heel prick test
- Antenatal: Molecular genetics
- Hb electrophoresis - diagnostic when above 90% HbS (number 4 has sickle cell)
FBC and blood film in sickle cell anaemia (4)
- Normocytic normochromic - normal in size and colour
- Increased reticulocytes
- Sickled RBC
- Howell Jolly bodies
Last resort treatment for sickle cell anaemia
Bone marrow transplant
Pathophysiology of sickle cell anaemia (5)
- Glutamic acid -> valine on 6th codon of beta-globin on chromosome 11
- Causes irreversible RBC sickling
- RBC more fragile so less efficient
- Bone marrow focuses more on reticulocytes, decreasing other cell lines (eg: causes neutropaenia)
- Intra+extravascular haemolysis
Presentation of sickle cell anaemia (2)
General anaemia symptoms + prehepatic jaundice
where globally and why is sickle cell most common
- Commonest in africa for antimalarial properties (vs plasmoduium falciparum)
What to give patients with sickle cell painful crisis? (4)
- IV fluids
- Analagaesia - NSAIDs
- Oxygen if low
- Broad spectrum antibiotics due to neutropaenia
infectious trigger of aplastic crisis
paravirus B19
if a patient experiences recurrent painful crisis what should be given
oral hydroxyurea / hydroxycarbamide
best diagnostic test
Hb electrophoresis
